1. Field of the Invention
The present invention relates to touch sensing technology and more particularly, to a touch sensing device 2D sensing information update method that stops from updating the 2D sensing information if the measured flatness index is larger than a predetermined positive flatness reference value or smaller than a predetermined negative flatness reference value that indicates the touch sensing panel of the touch sensing device is in an abnormal status, such as being covered by an external object for a long period of time.
2. Description of the Related Art
In order to comply with human intuition, touch sensing devices are widely used in modern electronic products, enabling the user to control electronic products conveniently by means of a touch of a finger or stylus.
Referring to FIG. 6, when a conventional touch sensing device A1 is started up, the driving and sensing circuit A12 of the touch sensing device A1 measures the capacitive coupling amount C (such as the capacitance value, current value, voltage value or amount of electrical charge) at each of all the sensing points A113 between the driving lines A111 and sensing lines A112 of the touch sensing panel A11 at the time no external objects (finger or stylus) touch the touch sensing panel A11, and then integrates the measured capacitive coupling amount C at each sensing point A113 and the coordinate data of the respective sensing point A113 into a respective 2D sensing information Ca, enabling the processor A13 of the touch sensing device A1 to update this 2D sensing information Ca to become a reference 2D sensing information Ca0 and then to store this reference 2D sensing information Ca0 in the memory A14 of the touch sensing device A1.
When an external conductive object touches or covers the touch sensing panel All of the touch sensing device A1, the capacitive coupling amount C at each sensing point A113 within the touched or covered area is relatively changed. Thus, the processor A13 can read in the reference 2D sensing information Ca0 from the memory A14, and then subtracts the reference 2D sensing information Ca0 from each measured capacitive coupling amount C to check the variation of the capacitive coupling amount at each sensing point A113 and to further determine the touch sensing status at each sensing point A113 of the touch sensing panel A11 subject to the variation of the capacitive coupling amount at sensing point.
However, if the capacitive coupling amounts C at some sensing points A113 of the touch sensing panel A11 of the touch sensing device A1 are changed just because the touch sensing panel A11 is accidentally covered by an external object (water drop or user's finger) for a long period of time, the processor A13 can use the 2D sensing information Ca obtained under an abnormal condition as a reference 2D sensing information Ca0 for further determining, leading to a false touch sensing condition determination.
Thus, how to prevent the processor A13 from using a 2D sensing information Ca obtained under an abnormal condition as a reference 2D sensing information Ca0 for determining a touch is an important subject to study in touchscreen technology.